This invention relates generally to a system for increasing the efficiency of internal combustion engines operating at high loads, and more particularly, to a multi-cylinder engine in which at least one cylinder is used as a power recovery device. The waste heat generated during the operation of the engine is utilized for producing an amount of energy to perform work by means of a Rankine cycle.
Diesel engines were developed to be highly reliable prime movers for transportation and stationary applications. It is generally well known, however, that while the efficiency of a diesel engine is somewhat better than that of other types of internal combustion engines, the efficiency of a diesel engine is still relatively low in terms of the conversion of the energy of the fuel consumed to energy output. At best, the mechanical power output of a conventional diesel internal combustion engine is only about thirty to forty percent of the rate at which energy is released in the combustion of the fuel. The remainder of the energy is lost to the environment primarily by the loss of heat energy from the hot exhaust gases and loss of heat through surfaces adjacent the combustion chamber. In many engines, most of the heat passing through surfaces adjacent to the combustion chamber is not transmitted directly to the environment, but is transmitted to a circulating stream of engine cooling fluid, which in turn transmits heat to the environment.
As a consequence of these inefficiencies, various systems have heretofore been proposed for recovering and utilizing the wasted heat energy from engines to generate useful power. Certain of the proposals have been for internal combustion engines with so-called "bottoming cycles" of various sorts, including Rankine cycles, where attempts have been made to extract energy from the engine exhaust gases. Such systems, however, have been beset with one or more of the following shortcomings. The system (a) is bulky and of complex construction; (b) uses a separate working fluid loop for the bottoming cycle, requiring a separate condensor and evaporator; (c) requires the use of, for example, steam turbines and reduction gears to supplement the basic engine output; (d) is quite costly and therefore is not commercially attractive to the industry; and (e) does not utilize the heat energy that is lost to the engine cooling fluid.